This application is based upon and claims the benefit of Japanese Patent Application No. 2000-243282 filed on Aug. 10, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a printed circuit board on which ICs are mounted, which is suitably used for electronics that are required to have a reduced noise level, such as an IC for controlling vehicle braking.
2. Description of the Related Art
Recently, various regulations have required a reduction in the noise level of ICs, a typical example of which is a central processing unit. In a conventional IC, two opposed pins (two terminals respectively disposed at opposed two sides when the IC forms a rectangle) receive a source potential and a ground potential, respectively. However, plural terminals are conventionally arranged for receiving the source potential and the ground potential in an IC, in view of noise regulations.
In such a case, because the number of required pins is increased, package size and the number of bypass-capacitors are increased. As a result, an area of a substrate occupied by the bypass-capacitors and wiring members for connecting them is increased.
Further, this effect lessens flexibility of substrate pattern design to make the noise countermeasures on the substrate difficult. As a result, the noise level may be raised on the contrary. Incidentally, it is conceivable that a multilayered substrate can solve the above-described problem; however, the multilayered substrate results in high cost.
The present invention has been made in view of the above problem. An object of the present invention is to decrease a noise level while suppressing an increase in occupied substrate area.
According to the present invention, in a printed circuit board on which a plurality of pins are arranged to form a generally polygonal shape, the pins includes a first pin as a ground terminal and a second pin as a source terminal. The ground terminal is disposed at a corner portion of the generally polygonal shape, and the source terminal adjoins the ground terminal. Further, a first conductive region extends radially from the corner portion of the polygonal shape and is electrically connected to the ground terminal.
Because the source terminal adjoins the ground terminal, a substrate area occupied by a bypass capacitor can be restricted from increasing. Further, because the ground terminal is electrically connected to the first conductive region, ground impedance can be lowered, resulting in noise reduction.